Method for verifying access authorization for voice telephony in a fixed network line or mobile telephone line as well as a communications network

ABSTRACT

A method for verifying access authorization for voice telephony in a fixed network line or mobile telephone line, as well as a communications network having such access authorization verification are described. The access authorization is verified by analysis of a voice signal which was entered by the subscriber placing the call, before or during a call in progress. In one variant, the voice signal is entered as a password before the connection is established; in another variant, voice signals are analyzed for voice recognition and subscriber identification, the same voice signals also being transmitted to the person being called, making concealed access verification possible which does not hamper the normal flow of conversation.

FIELD OF THE INVENTION

The present invention relates to a method for verifying accessauthorization for voice telephony in a fixed network line or mobiletelephone line as well as a communications network having such accessauthorization verification.

BACKGROUND OF THE INVENTION

In the case of private branch exchanges (PBXs) for telecommunicationshaving a large number of extension stations used by different persons,but also in the case of mobile terminals such as cell phones, thereexists the problem of abuse by unauthorized third parties or byunauthorized employees of a company. For example, personal conversationsare frequently held via PBX lines of large corporations at theemployer's expense. Moreover, when telephone calls are made from astolen or lost mobile telephone, the account of the lawful owner isalways charged without the owner being able to directly prevent this.

To prevent unauthorized use in private branch exchanges, methods areknown in which the user of a terminal must enter an access code to beable to make an interoffice call and/or to dial specific outsidenumbers. In these methods, the subscriber enters a personal access code(PIN) via the keypad of the terminal, the access code being evaluated bythe private branch exchange and compared with a table of authorizednames. This method also makes it possible to allocate the incurredcharges to specific individuals. Once the subscriber's authorization hasbeen established in this manner, the corresponding PBX line is enabledto establish an interoffice or long-distance connection.

However, due to the additional time required, this method of entering acode before each call is very cumbersome and is not practical for PBXlines from which many calls are made regularly, e.g., a secretary'soffice or a senior executive's office. For that reason, such lines arefrequently exempted from the access verification so that any person cancall from them at any time and the problem of unauthorized use persists.

An additional known method is to detect unauthorized use after the factby analyzing the call durations, the direction, and the subscriber orthe number called. For this purpose, the private branch exchange logsthe calls made, the call destinations, call duration, and the associatedPBX line. A similar verification takes place in the network managementsystem of a public switched telephone network. For example, all callslasting longer than a predetermined duration are checked for the calldestination later or during the connection. An unauthorized use can bedetected if the call destination cannot be assigned to a predeterminedgroup of telephone numbers, which, for example, are assigned to thecompany's customers. Individual PBX lines such as those of seniorexecutives can be exempted from checking for unauthorized use in thiscase also.

However, even with this type of checking for unauthorized use, onlyline-specific determination of an unauthorized use is possible. Thosecases in which the same person improperly uses different terminalswithout authorization cannot be detected. Moreover, the unauthorized usecan only be detected after the fact; an unauthorized call cannot beprevented.

U.S. Pat. No. 5,623,539 relates to a device and a method for monitoringa telephone connection for unauthorized use. For this purpose, voicesamples of all of the persons who are authorized to use the telephoneconnection are stored. During a conversation conducted over thetelephone connection, the transmitted voice data is tapped and brokendown via suitable means into individual voice samples, each of thethus-obtained voice samples corresponding to the voice of one of theconversation participants. These voice samples taken from the telephoneconversation are compared to the stored voice samples. The telephoneconnection is only accepted as authorized when a sufficient matchbetween at least one of the stored voice samples and at least one of thevoice samples obtained from the telephone conversation is determined.

U.S. Pat. No. 5,093,855 relates to a method and a device for speakerrecognition in a telephone switching exchange, where tapped speechsamples are supplied via the telephone line to the exchange, where theyare compared to previously stored speech samples. If the speaker isrecognized, a first signal is emitted, otherwise, a second signal isemitted.

The publication “Speaker Identity Verification over Telephone Lines:Where we are and where we are going” by T. C. Feustel and G. A. Velius,International Carenaham Conference, Zurich 1989, addresses voicerecognition and the security, e.g., against unauthorized telephone use,that it can provide. In this context, the possibility to increasesecurity by combining voice recognition and the use of passwords or PINsis also mentioned.

SUMMARY OF THE INVENTION

The present invention provides a method for verifying accessauthorization for voice telephony that does not hamper the normal use oftelephones and permits direct detection of attempts at unauthorized useand prevents them if necessary. In particular, the method of the presentinvention provides a method for verifying access authorization for voicetelephone in a fixed network or mobile telephone line by voicerecognition.

According to an embodiment of the present invention, voice signals of asubscriber placing a call are recorded before or after the communicationconnection to the subscriber being called is set up. For example, thesubscriber can be automatically prompted to acoustically provide apassword after dialing the outside number, but before the connection isestablished. Alternatively or in addition to this embodiment, the voicesignals can be recorded during the course of the call, the voice signalsof the subscriber placing the call being relayed concurrently to thesubscriber called so that the communication is not disturbed. In bothcases, the voice signal of the subscriber placing the call is analyzedby voice recognition algorithms and compared with a reference datarecord or several reference data records for purposes of assignment. Thereference data record(s) is/are assigned to the fixed network line ormobile telephone line in an unambiguous manner; in particular, theydefine the group of persons having authorized access. According to thepresent invention, the communication connection can be automaticallydisconnected or not established and/or an alarm can be triggered, if therecorded voice sample cannot be assigned to any reference data record.Otherwise, the communication connection can be maintained or establishedin the customary manner.

In a further embodiment, the voice recognition can take place after thestart of the communication connection online, i.e., directly during thecommunication connection. As with line tapping by police or intelligenceservices, the voice signals of the subscriber placing the call aretapped from the data line and supplied to a voice recognition unit,which analyzes them online. The voice data is transmitted concurrentlyto the person called. If the voice recognition unit is able to make anassignment to a reference data record, the analysis of the voice signalis terminated, and the data processing capacity of the voice recognitionunit is available for identifying additional callers.

As an alternative to voice recognition during the connection, thespeaker can be assigned to a billing account before the connection isestablished as part of an authentication procedure that the speaker mustundergo. In this case, the telephone user is requested to provide avoice sample, and the connection is only established once the voicesample has been identified and the speaker is identified as authorized.

In addition to online voice recognition, the voice signal of thesubscriber placing the call can also be recorded and stored inintermediate memory as a voice sample. The stored voice sample is thenanalyzed during or after the communication connection.

In embodiments of the present invention, it is not necessary to performthe cumbersome action of entering a password manually before thecommunication connection is established, but rather access isestablished and/or maintained by voice control. When accessauthorization is verified after the connection has been established, theprocess takes place concurrently with the normal flow of the call; theparticipants do not notice the access verification, but rather they areable to talk over the telephone in the normal manner, thus saving time.The same voice signals that are transmitted to the person called areanalyzed for voice recognition and subscriber identification. This doesnot interfere with the transmission of voice signals between theconversation participants. Thus, in principle, any connection can bemonitored for unauthorized use without interfering with the normal flowof telephone conversation by additionally entering access codes.

Several possibilities for voice recognition are known and can be used toimplement the present invention. There are voice recognition algorithmsfor recognizing semantic content of speech that compare an actual voicesample with an already stored voice sample corresponding to a specificspoken word. In this context, the stored voice sample corresponds, forexample, to a spoken word whose text representation is also stored. Bydetermining a correspondence between the actual and the stored voicesample, it is possible to assign a textual representation, e.g., in theform of an ASCII representation, to the actual voice input, thus inprinciple making it possible to recognize the content of a voicemessage. Such voice recognition units are used, for example, for thevoice control of computers and the like.

Or, the future user inputs the stored voice sample during a trainingphase. Thus, only the actual voice input of this user may be reliablyrecognized by the voice recognition, since even voice samples ofdifferent users that have the same semantic content vary due toindividual speech patterns.

This technique can also be used in a refinement of the present inventionto verify access authorization for a telephone line. In this connection,the reference data records are reference voice samples corresponding tospecific words spoken by one person, e.g., typical greetings, the firstor last name of a person having authorized access or other expressionswhich frequently occur in a telephone conversation. These voice samplesare recorded in a training phase and stored in digital form in a memoryas a reference data record. In order to implement the method, the voicerecognition algorithms analyze the recorded voice data for theoccurrence of fragments, i.e., individual words or expressions thatmatch the reference voice sample within a specified tolerance range. Inthis connection, it is not the semantic content of the reference or ofthe actual voice signal that is of significance, but rather theindividual speech pattern of the authorized and the calling personswhich is expressed in a specific characteristic pattern of the referencevoice sample.

Another embodiment of the present invention also provides for theanalysis of the input voice signals for speech patterns that arecharacteristic of the user regardless of their semantic content. Thespecific intonation, voice register, dialect, and the like, which causethe voice of a person to appear nearly unique to the human ear, aremanifested in characteristic features of a voice sample taken from thisperson, e.g., a specific frequency distribution, which can be used toidentify this person by electronic means. Therefore, according to thepresent invention, reference speech patterns, e.g., frequency patternsor amplitude patterns, which are characteristic of one person, arestored as reference data records. For example, they can be obtained bystatistical analysis of a voice sample using a corresponding voicerecognition algorithm. To identify the actual voice sample recordedduring a call, the voice recognition algorithms then create acorresponding speech pattern by statistically analyzing the sample. Inthis connection, statistical analysis primarily refers to a frequencyanalysis in which the tone and voice register of the speaker can beidentified; dynamic analysis refers to the dynamics of the voice signal,i.e., the amplitude characteristic and, accordingly, a specificintonation. Both methods are suitable for identifying a speaker. Thisspeech pattern is then compared with the reference speech patterns. Itis determined whether the characteristic features of both patternsagree. In creating the reference speech pattern from a reference voicesample, the same voice recognition algorithm is used as that which withthe actual voice sample is analyzed.

In this embodiment of the present invention, the analysis of theindividual speech patterns can make a significantly more accurateidentification of the speaking person possible than the search forspecific words which, although individually characterized, may notalways be reliably detectable due to the shortness of the words. Thefirst variant is particularly suited for access verification by enteringa specific spoken password, while the second variant is particularlysuited for covertly verifying the access authorization during an ongoingcall.

In a further embodiment, the reference data records correspond to thegroup of authorized persons, e.g., all the employees of a company whomust make telephone calls as part of their work activity. The referencedata records are stored, for example, in a table of authorized names. Inthis context, one person can be authorized only for selected telephonenumbers or types of connections, or authorization can change as afunction of the time of day.

The method according to the present invention can further prevent theuse of terminals for the placement of toll calls by persons notbelonging to this authorized group, while any authorized person canplace calls from any PBX line of the company.

In another embodiment of the present invention, the access authorizationcan further differentiated according to PBX lines. The reference datarecord or reference data records are unambiguously assigned to a PBXline of a private branch exchange. The reference data record orreference data records, in turn, define the group of authorized persons,in this case for a single PBX line. This makes it possible to preventpersons authorized per se from placing telephone calls from otherterminals. This is useful in the event that individual lines are clearedfor interoffice calls but not for long distance calls, while thislimitation does not exist for other PBX lines.

In the event of an access verification during the connection, the voicesignals can be tapped during a predetermined time interval, e.g., 30 to60 seconds, the recording starting in particular immediately after theconnection is established. The voice sample is already analyzed duringthe tapping or at the end of the time interval.

For reasons of data security and privacy, the recorded and possiblybuffered voice sample is erased after the voice recognition iscompleted, if it was possible to assign the sample to a reference datarecord. However, in the case of unauthorized use, i.e., no automaticassignment can be made to a reference data record and, accordingly, toan authorized person, the voice data preferably remains stored. It canthen be used to identify the speaker.

In order to keep the expense for verifying access authorization as lowas possible, the method can be implemented only at certain times of theday and/or week and/or only via specific call destinations, e.g., onlyfor long-distance connections. The fixed network or mobile telephoneline in question, or individual PBX lines of a fixed network line arethen completely blocked or completely cleared for connections outside ofthese time periods or for other call destinations.

Moreover, it is provided that the access verification by voicerecognition is not implemented if, before a connection is established,the user enters a key combination, e.g., a PIN code or an acousticsignal, e.g., a sequence of MFC signals, and has his authorizationverified via this access code.

A further embodiment of the present invention provides that the numberof unauthorized access attempts is recorded and the line is blocked ifmore than a predetermined number of such attempts is detected within apredetermined time interval, e.g., one day or one hour. In addition, analarm can first be triggered via the network management system, and anoperator can be switched in.

A further embodiment of the present invention can involve acommunication network having a plurality of fixed network lines ormobile telephone lines, as well as technical means for establishing acommunication connection between two or more lines of the same or of adifferent communication network, including:

-   -   a) means that are capable of accessing a data line via which        voice signals are at least partially transmitted from the        calling line to the called line, and that are capable of        recording a voice signal transmitted by the calling line;    -   b) at least one memory in which reference data records are        stored which are assigned to a group of persons having access        authorization; and    -   c) at least one control unit having a voice recognition unit        which is capable of accessing the memory for the reference data        records, analyzing the tapped voice signal via voice recognition        algorithms, and determining the access authorization of the        subscriber placing the call by comparison with the reference        data records, the control unit initiating the production of a        signal to disconnect the connection if the voice signal cannot        be assigned to any of the reference data records,        so that voice samples are recorded at regular time intervals        during the entire communication connection, and the speaker's        authorization is checked at regular time intervals.

In this context, a communication network can be understood to be thetotality of all lines including the exchanges or conversion stations andpossibly data lines and other intelligent switching and transmissiondevices. The elements involved in the present invention can, however, bearranged in only a small part of the network, e.g., in a private branchexchange. The communication network according to the present inventionadvantageously makes it possible to verify the access authorization ofusers of individual lines and accordingly to implement the methodaccording to the invention.

In order to be able to utilize the voice signals in a detected case ofabuse, to identify the unauthorized caller or for offline voiceanalysis, the communication network may have at least one memory inwhich the recorded voice signals are stored in intermediate memory asvoice samples.

According to the present invention, the verification of accessauthorization within the communication network can take place at variouspoints within the network. If the access authorization of users of aprivate branch exchange is to be verified, the control unit and thereference data memory or possibly the voice sample memory can bearranged within the private branch exchange. The control unit can be,for example, part of a data processing system that logs the connectionsmade by the individual PBX lines, blocks individual PBX lines on atime-dependent basis or for specific call destinations, and possiblyrequests a PIN code.

Alternatively, the control unit and the corresponding memory locationscan be located outside the customer area in an exchange in the actualtelephone network. In this case, the reference data of the linesassigned to the exchange can be stored in the reference data memory.Preferably, the reference data is stored in a line-specific manner, sothat an authorized group of persons is defined for each line and ischecked by the exchange. If the control unit is unable to assign thevoice sample to any of the reference data records, it causes theexchange to generate a signal disconnecting the connection. In thismanner, a common control unit can be used to centrally verify the accessauthorization of users of a plurality of lines in the exchange withoutrequiring a modification of the lines on the customer side.

Access verification can be further centralized by assigning the controlunit and the corresponding memory to an SCP (Service Control Point) ofan intelligent network and by the control unit causing the SCP togenerate a signal interrupting the connection if the voice sample cannotbe assigned to any of the reference data records. The so-calledintelligent network is an open communications network, which is built onthe traditional telephone network and makes various telephone serviceshaving new features possible, for example, toll-free calling usingspecific numbers or reaching various offices of a corporation using adial number that is identical over a larger region. The central computercontaining the required switching information is known as the SCP. Thetransition from a telephone network of one network provider to that of adifferent network provider is also accomplished using structures similarto an IN.

In addition, the method according to the present invention can also beused to check the authorization of a mobile terminal user. For thispurpose, a mobile terminal for telecommunications is proposed,including:

-   -   a) means that are capable of accessing a data line, via which        voice signals are transmitted in electronic form, and of        recording an entered signal and a voice signal;    -   b) at least one memory in which at least one or more reference        data records are stored which are assigned to a group of persons        having access authorization; and    -   c) at least one control unit having a voice recognition unit        which is capable of accessing the memory for the reference data        records, analyzing the tapped voice signal via voice recognition        algorithms, and of determining the access authorization of the        subscriber placing the call by comparison with the reference        data records, the control unit initiating the production of a        signal to disconnect the connection or causing the terminal to        shut off if the voice signal cannot be assigned to any of the        reference data records,        so that voice samples are recorded at regular time intervals        during the entire communication connection, and the speaker's        authorization is checked at regular time intervals.

The reference data record(s) can be stored on the chip of a mobiletelephone card. The owner of the mobile telephone can provide the voicesample necessary for this purpose when purchasing the mobile telephonecard. Therefore, a lost mobile telephone is, in principle, operable, butthe mobile telephone card is only operable as a function of the correctspeech pattern. This can prevent calls from continuing to be made on alost mobile telephone at the owner's expense.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of the sequence of operations of an embodimentof the present invention;

FIG. 2 shows a flowchart of another embodiment of the present invention;

FIG. 3 a shows a communication network used with an embodiment of thepresent invention;

FIG. 3 b shows a communication network used with an embodiment of thepresent invention;

FIG. 4 a shows a communication network used with an embodiment of thepresent invention;

FIG. 4 b shows a communication network used with an embodiment of thepresent invention;

FIG. 4 c shows a communication network used with an embodiment of thepresent invention; and

FIG. 5 show a communication network used with an embodiment of thepresent invention.

DETAILED DESCRIPTION

FIG. 1 schematically shows a sequence of operations of an embodiment ofthe method of the present invention. At the start of the method,subscriber A calls a destination number. The connection is establishedas soon as subscriber B answers. Typically, both subscribers begin tospeak. The voice signals of subscriber A are automatically tapped andanalyzed, the analysis lasting a predetermined time span, approximately30 seconds to one minute. A interoffice trunk, via which the voicesignals between both users are transmitted, is accessed withoutinterfering with the transmitted signal, so that the access verificationdoes not affect the conversation.

The voice signal of subscriber A is analyzed, i.e., compressed by voicerecognition algorithms, the thus-produced speech pattern being comparedwith reference data records stored in a table of authorized names. Ifthe actual voice signal can be assigned to one of the reference datarecords, then the subscriber is considered to be authorized and entitledto call. In this context, the table of authorized persons can referspecifically to the line as a whole or to a PBX line and/or it may betime-dependent.

If subscriber A is approved, then the connection is maintained until theend of the call. In the simplest case, no additional check is made. Tofurther increase security against abuse, the process is repeated atregular time intervals, i.e., the voice signal of subscriber A isanalyzed again.

If the subscriber is identified as unauthorized, because his voicesignal cannot be assigned to an entry in the table of authorizedpersons, the connection is interrupted in the simplest case bygenerating a interrupting signal or by briefly deactivating theterminal. A new connection can be established immediately after theconnection is terminated.

To counteract persistent attempts at unauthorized use, it is alsopossible to record the number of attempts at unauthorized use within aspecific time interval and to set a critical value for the maximumnumber to be tolerated. If the number of attempts at unauthorized useexceeds this value, a total block of the line is automaticallyinitiated. The line can then only be enabled again after a specificwaiting period or by the entering an enabling code. In addition, as inthe case of a normal termination due to unauthorized use, an alarmsignal can be produced at the telephone itself or at a PBX operatordesk.

FIG. 2 shows an additional flowchart of the method according to thepresent invention. Before the method is initiated, all users of thetelephone line to be protected against abuse enter voice samples intothe system. The voice recognition unit or a speech pattern recognitionsystem extracts the subscribers' speech patterns and stores them,compressed by a voice recognition algorithm, in memory as referencedata. The reference speech patterns are, thus, available for onlinerecognition at the facilities of the network provider, in a privatebranch exchange, or on the calling card of a mobile telephone.

The process begins once a caller initiates a call from a telephone, thetelephone connection is established by the network provider, and thetelephone conversation is started. At the same time as the telephonecall, the speech pattern recognition is initiated to determine thespeech pattern of the caller. This speech pattern determined for thecaller from the telephone call is compared with the reference stored forthis line or on the calling card of a mobile telephone.

If a speech pattern is recognized, i.e., the actual voice signal matchesa reference, the speech pattern recognition for this connection isdiscontinued, and the computer capacity can be used to analyze othercalls.

If no speech pattern is recognized, the call is interrupted to protectthe customer from financial loss. When a mobile telephone is used with acalling card, the call is always terminated. If necessary, the customercan be provided with a log of the attempt at unauthorized use in orderto identify the person using the telephone without authorization.

FIGS. 3 through 5 show three possibilities for implementing the methodaccording to the present invention in a communications network.

For this purpose, FIG. 3A shows a private branch exchange (PBX), whichis connected to a public switched telephone network. The private branchexchange (PBX) has a plurality of extension stations, of which three areshown here. The access authorization of the users of the individualextension stations is to be monitored according to the presentinvention. For this purpose, an IP (intelligent peripheral) is assignedto the private branch exchange (PBX), the IP being capable of accessingthe telephone line via which signals are transmitted from one extensionstation to an additional line outside the private branch exchange, andof recording and storing the signals entered by the extension stationuser. In addition, the IP has a voice recognition unit that is capableof analyzing the recorded voice signal and comparing it with previouslystored reference data records. In addition, the IP is also capable ofaccessing the reference data record memory. In this case, eitherspecific reference data records are assigned to each extension station,the reference data records being assigned to the users of this extensionstation, or the table of authorized persons contains all potential usersof the entire private branch exchange irrespective of the actual PBXline.

If the IP cannot match the actual voice sample to any of the referencedata records, it applies a suitable control signal to induce the privatebranch exchange (PBX) to generate a signal interrupting the connection.As a result, the connection of a PBX line to a user in the publicswitched telephone network via the private branch exchange isinterrupted.

FIG. 3B shows an example for the implementation of person-specificassignment of charges by voice recognition in a private branch exchange.

In the private branch exchange, in the case of proceduralauthentication, i.e., voice recognition before a connection isestablished, all calls originating from the terminals connected to PBXlines (ports 22 to 28) are redirected to one port (port 21 in theillustrated example). This redirection is performed by the control unitof the private branch exchange. The relevant programs are stored, forexample, in a memory module, an EEPROM in this case. A digital signalprocessor (DSP) having suitable voice recognition software and,optionally, voice recognition hardware is connected to port 21. If theidentification is positive, it relays the signal to the private branchexchange via the customary control functions, i.e., either via the line,a V.24 interface, or another management interface. The thus-verifiedcalls are switched from the private branch exchange (PBX) to theinterexchange trunk and form an outgoing call. The billing informationfor person-specific cost assignment is fed directly into the billingsystem.

In the case of online recognition of the speaker, the call is alreadyset up; however, as in the case of “bugging” a call, the callinformation is serially routed through the DSP. The DSP analyzes thespeech without interfering with the transmission and relayscorresponding information to the private branch exchange or the billingsystem.

FIG. 4A shows an arrangement of control unit IP corresponding to thearrangement of FIG. 3A in an exchange. A connection from the subscriberline to an additional line in the public switched telephone network isestablished via this exchange. Physically and organizationally, theexchange is assigned to the subscriber line; however, it is notnecessarily located in its immediate vicinity. Aside from the differentphysical arrangement of the IP, the access verification is performedhere in the same manner as described above. The difference is that nointelligent devices for voice recognition and for speech storage need tobe provided on the subscriber side, since these are centrally integratedin the exchange.

FIG. 4B shows an example for the implementation of access verificationby voice recognition in an exchange of a telephone network.

Voice recognition system IP can be implemented in a computer, forexample in the form of a plug-in module in the exchange. Calls for whichthe speaker is to be identified are routed from the exchange through theIP.

Voice recognition is implemented either in dialog form, i.e., anauthentication procedure is executed as described above in FIG. 3B, orelse the voice is recognized online. In the latter case, the speechpattern is checked during the conversation in progress andcharacteristics of the speech of speaking user A are compared with thestored patterns. In this case, the call is tapped, so to speak, by theIP without interfering with it.

One possible structure for the authentication procedure is a dial-ininto the DSP of the IP. For this purpose, the telephone channel isrouted to an input of the IP. At this point, subscriber A is asked bythe software of an intelligent voice response system to state his nameor his identifier. After that, he is asked for his password or hispersonal identification number PIN. The data is compared with theidentifier stored in memory, and the speech pattern is compared with thestored patterns either using frequency spectra or speech dynamics. Inthe dialog form, the implementation of voice recognition is very simple,since the identifier is made up of precisely defined words, which werepreviously entered.

After authentication in the IP, the customer is directed to a menu thatrequests that he enter the desired telephone numbers. These are recordedas in conventional messaging or voice response systems, converted intopulse or MFC dialing information, and sent into the network, or they arerelayed to the exchange as signals in the format of signaling system No.7 (Common Channel Number 7, CCS7). The exchange then initiates theconnection to subscriber B. The use of CCS7 signals permits fasterprocessing and more features, namely all those implemented in CCS7 andcleared for the IP.

The information concerning the speaker, i.e., the identified referencedata record, is sent as control information to the exchange via theCCS7, and generates an alarm in the network management system. Thenetwork management system can also generate a corresponding alarmmessage regarding call data records, so that the billing system alsoreceives appropriate information.

The speaker-identifying data records produced in this way are used foraccess verification; however, they can also be used for billing a call.The corresponding procedures are described in the flowcharts.

When recognizing continuous speech, the system preferably concentrateson the essential characteristics of the language. To be sure, key wordssuch as “good morning, hello,” etc. can be considered in the entryprocedure; however, in principle, it is necessary to storespeaker-specific characteristics, irrespective of which language andwith whom the user is speaking. For this purpose, the algorithm can usestatic methods such as frequency spectrum analysis, as well as dynamicspeech characteristics.

FIG. 4C shows an additional example of the method according to thepresent invention implemented in an exchange. The subscriber unit(subscriber card) of subscriber A recognizes whether the subscriber hasprovided voice recognition for access verification. The centralprocessing unit CPU of the exchange initiates the appropriate routingthrough the switching matrix, the actual switching unit. As a result,the call is not routed directly to subscriber B or to the next exchange,but rather it is first routed through an intelligent peripheral IPhaving a digital signal processor (DSP). The output port of the IP isrouted through the switching matrix to subscriber B or to the nextexchange.

All control information and, accordingly, also the result of the voicerecognition are compared in the exchange having the central processingunit CPU.

The IP can also include several voice recognition units or DSPs and,thus, analyze several lines simultaneously. The information concerningthe usage of the IP and concerning the analytical results is transmittedto the CPU.

FIG. 5 shows the implementation of the method according to the presentinvention in the service control point SCP of an intelligent network.

When implemented in the IN, the voice data is routed via an ISDN channelto voice recognition unit IP, which is located at the site of the SCP.Control information, for example, whether the calling line is usingvoice recognition for monitoring abuse, results from the voice analysis,and the like are then exchanged between the SCP and the serviceswitching point SSP, which is located at the site of the exchange.

Implementing the method according to the present invention in thecentrally structured IN makes it possible to centrally implementvoice-based abuse control over a large network area, i.e., a pluralityof lines. This eliminates the need for expensive software and hardwareequipment in the exchanges; only the IN must be adapted. Thisimplementation is, therefore, suitable in particular for cases of lowdemand or in the introductory phase, i.e., it is not yet worthwhile toequip each exchange.

The present invention is suitable, in particular, for operators ofcommunication networks to increase the security of voice telephonycustomers against abuse. Moreover, the present invention is particularlysuitable for operators of private branch exchanges where the problem ofunauthorized access is encountered on a regular basis.

1. A method of verifying access authorization for voice telephony for afixed network line or a mobile telephone line, comprising: providing afirst voice signal of a first subscriber placing a telephone call;analyzing the first voice signal via a voice recognition algorithm whenone of (a) before a communication connection between the firstsubscriber and a second subscriber is established and (b) after thecommunication connection between the first subscriber and the secondsubscriber is established, and if the analyzing begins after thecommunication connection between the first subscriber and the secondsubscriber is established then the first voice signal and a second voicesignal of the second subscriber continue to be relayed; comparing thefirst voice signal with a voice reference data record to determine anidentity of the first subscriber; determining if the first voice signalis in the voice reference data record and if the first voice signal isnot in the voice reference data record then at least one communicationeffect occurs, the at least one communication effect including notestablishing the communication connection, automatically interruptingthe communication connection and generating an alarm in thecommunication connection; recording the first voice signal before andafter a communication connection to the second subscriber isestablished; assigning the voice reference data record to the fixednetwork line or the mobile telephone line; and recording a voice sampleof the first subscriber and the second subscriber at regular timeintervals during the communication connection and checking the first andsecond voice signals with the voice reference data record.
 2. The methodof claim 1, wherein the voice reference data record contains referencevoice samples corresponding to at least one specific spoken word, andthe voice recognition algorithm analyzes a recorded voice signal withthe reference voice samples for a match within a determined tolerancerange.
 3. The method of claim 1, wherein the voice reference data recordcorresponds to a reference speech pattern independent of semanticcontent and characteristic of a person, and the voice recognitionalgorithm creates a corresponding speech pattern from the recorded voicesignal by statistically analyzing the recorded voice signal, thecorresponding speech pattern being compared with the reference speechpattern.
 4. The method of claim 3, wherein the reference speech patternis characteristic of a specific frequency distribution of spokenlanguage by the person.
 5. The method of claim 1, wherein the referencedata record is assigned to a PBX line of a private branch exchange. 6.The method of claim 1, wherein the recorded voice signal is recordedduring a predetermined time interval after the initiation of thecommunication connection, and the recording is terminated at aconclusion of the communication connection.
 7. The method of claim 1,wherein the recorded voice signal is stored in an intermediate memory,and further comprising erasing the recorded voice signal stored in theintermediate memory if the recorded voice signal is determined asmatched with the reference data record, and continuing to store therecorded voice signal if the recorded voice signal is determined asnot-matched with the reference data record.
 8. The method of claim 1,wherein the method is actuated only at at least one of a predeterminedtime of day, a predetermined time of month, and a predetermined calldestination, and the communication connection cannot be establishedduring at least one of a time outside the predetermined time of day, atime outside of the predetermined time of month, and a call destinationoutside of the predetermined call destination.
 9. The method of claim 1,further comprising assigning a predetermined authorization code to thefixed network line or the mobile telephone line and if the firstsubscriber enters the predetermined authorization code before thecommunication connection is established then the method is not actuated,the first subscriber entering the predetermined authorization code by atleast one of an acoustic signal and via a key pad.
 10. The method ofclaim 1, further comprising recording an amount of an attempt ofunauthorized access of the fixed network line or the mobile telephoneline and blocking the access of the fixed network line or the mobiletelephone line if the amount of the attempt of unauthorized access isequal to or larger than a predetermined maximum attempt value within apredetermined time interval.